Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $69.62   10.384%   $76.8493   $76.85   $76.85   $76.80  
  Purchase #2 $238.33   3.350%   $246.3141   $246.31   $246.30   $246.30  
  Purchase #3 $21.67   4.380%   $22.6191   $22.62   $22.60   $22.60  
  Purchase #4 $166.93   4.564%   $174.5487   $174.55   $174.55   $174.50  
  Purchase #5 $133.47   11.444%   $148.7443   $148.74   $148.75   $148.70  
  Purchase #6 $217.83   13.267%   $246.7295   $246.73   $246.75   $246.70  
  Purchase #7 $138.90   9.196%   $151.6732   $151.67   $151.65   $151.70  
  7 purchase totals = $986.75       $1,067.4782   $1,067.47   $1,067.45   $1,067.30